The regulation dopamine-sensitive adenylate cyclase was studied in nucleus caudatus, nucleus accumbens, hippocampus and cerebellar cortex of control and schizophrenic brains. The adenylate cyclase activity in the dopamine-rich brain areas of schizophrenics was more enhanced by SKF 38393, NaF or GppNHp than in similar areas of control brains. In contrast, NaF and cholera toxin stimulated adenylate cyclase in cerebellar cortex and hippocampus of controls and schizophrenics to the same extent. The present results suggest that the functional efficiency of the G/F protein that facilitates adenylate cyclase activation is increased in dopamine-rich brain areas of schizophrenic subjects.